1. Field of Invention
The invention relates to a driving-control device and a driving-control method of a backlight module, and, in particular, to a driving-control device and a driving-control method of a backlight module having a sequential flashing function.
2. Related Art
Nowadays, liquid crystal displays (LCD) are being used widely. They can be found on computer monitors, touch-screens for man-machine interface and home televisions. As popularity grows, its technical performance becomes more demanding in parameters such as viewing angle, contrast ratio, color saturation, and response time.
Among all the performance parameters, quick response time has always been one of the most sought-after items in improving motion picture quality. Low quality LCD with slow response time often causes picture blurring while viewing moving objects. This may not be a major issue if the LCD is just for a desktop computer monitor on which most of the pictures are still all the time. However, if the LCD is for home televisions, quicker response time is a must.
Besides the response time, there is a fundamental technical issue, the display type (or mode), that limits the LCD motion picture quality. The CRT display device, the predecessor of LCD, displays pictures by tracing out the images on a glass screen with a single scanning electron beam. Therefore, at any given moment, only a small fraction of the glass screen will be lightened while being scanned across by the electron beam. CRT display device cannot hold still the complete picture to be displayed on the glass screen. Actually, it displays pictures dot-by-dot and line-by-line. This is referred to as impulse-type display. LCD displays pictures in a different way. The LCD screen is composed of numerous pixels arrayed in rows and columns. Each pixel stores a graphic data. To display a picture, the LCD screen loads pixel data of a complete frame in parallel. Each pixel keeps its graphic data until being reloaded. At any given time, every pixel of the entire screen is lightened. Hence, LCD can hold still the complete picture to be displayed, so it displays pictures frame-by-frame. This is referred to as holding-type display.
A major drawback of holding-type display is the picture blurring caused by frame switching when displaying moving objects. Because the previous frame will never completely disappear from the screen before the next frame comes in. The most straightforward way to solve this problem is to make the previous frame disappear completely by inserting an extra dark frame before the next frame comes in. This will require some efforts on graphic processor. Another simpler solution is to shut off the backlight module of the LCD device for a specific period of time to create a momentary dark image. This dark image neutralizes human eyes from the previous frame and makes them ready to accept the next one. This is referred to as flashing backlight technology. To further eliminate blurring of holding-type display and mimic impulse-type display, an LCD backlight module is divided into several light zones. Each zone can be turned on and off sequentially. A specific control timing sequence is used to turn on and off each light zone. This timing sequence is synchronized to the frame data reload timing to optimize the motion picture quality. This is referred to as sequential flashing backlight technology. Since this sequential flashing backlight technique turns on and off a number of individual light zones, this can also be applied to power-saving and brightness-dimming control.
In some related arts, analog phase delay array is adopted to do the backlight on/off control. However, the timing sequence is adjusted by altering resistance or capacitance value of the control circuit. Therefore, it is an important subject to provide a digital programmable control for making the timing adjusting easier.